Heretofore it has been known to alert a gasoline station operator that leaks or spills were occurring from a service station dispenser. One such apparatus is shown in U.S. Pat. No. 4,842,163 issued on June 27, 1989 to Bravo. This apparatus utilizes a gasoline collector pit box and a float mechanism disposed therein to shut off the flow of gasoline when a predetermined amount of gasoline accumulates in the bottom of the pit box. The pit box and float mechanism are mounted below the level of the island. Although this device amplifies the effect of accumulation by slanting the bottom wall of the pit box and by increasing the length of the pivot arm to which the float is attached, it still requires the accumulation of too much gasoline and its associated harmful vapors before shut down occurs. The accumulation of vapors within the pit box creates a situation which is extremely dangerous to anyone who attempts to service these pumps and restore them to satisfactory operation.